John Broster and Allison Chambers
Graham Centre for Agricultural Innovation (NSW Department of Primary Industries and Charles Sturt University), Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678, Australia. Email: email@example.com
Weed control in the rice industry has been dependent on very few herbicides. Significant levels of resistance have been reported to one of the major herbicides (bensulfuron or Londax®). Random surveys were undertaken in both 2016 and 2017 in which the densities of the weed species were estimated. Additionally, screenings from rice samples analysed by the AGS Quality Appraisals Centre at Leeton were obtained. These screenings were further sorted to determine the quantity and species of weed seeds in the delivery samples. From the AGS Quality Appraisals Centre samples it was estimated that 150 billion barnyard grass seeds were delivered to silos during the 2017 harvest. This shows that while populations may not be resistant there are surviving plants setting seeds and those seeds not delivered to silos are replenishing the seed bank. In subsequent seasons the plants germinating from this seed bank are placing selection pressure for resistance development on the herbicides used for their control.